Octane, gasoline

Chemical Structures Effective in Improving the Gasoline Octane Number... 

The trend in d and has also been accompanied by improvements in product quality illustratisd by the increases in gasoline octane numbers and diesel oil cetane numbers. 

We cite isomerization of Cs-Ce paraffinic cuts, aliphatic alkylation making isoparaffinic gasoline from C3-C5 olefins and isobutane, and etherification of C4-C5 olefins with the C1-C2 alcohols. This type of refinery can need more hydrogen than is available from naphtha reforming. Flexibility is greatly improved over the simple conventional refinery. Nonetheless some products are not eliminated, for example, the heavy fuel of marginal quality, and the conversion product qualities may not be adequate, even after severe treatment, to meet certain specifications such as the gasoline octane number, diesel cetane number, and allowable levels of certain components. 

The Optimum level of gasoline octane is a complex function of a number of factors involving the customer as well as the automotive and petroleum... 

The procedure for measuring the cetane number of diesel fuel (ASTM D613) is similar to that used for measuring gasoline octane number. Cetane... 

In 1997 a total 1.3 billion gals of ethanol fuel was produced in the United States. Proposed new low sulfur conventional gasoline standards could greatly increase the demand for ethanol since desulfurization may lower gasoline octane. Almost all fuel ethanol is used as gasohol, but some is used to make E-85 (85% ethanol and 15% gasoline). E-85 can be used in flexible-fuel vehicles (FFVs) which can operate on gasoline or ethanol blends of to 85 percent ethanol. 

The major use of methyl chloride is to produce silicon polymers. Other uses include the synthesis of tetramethyl lead as a gasoline octane booster, a methylating agent in methyl cellulose production, a solvent, and a refrigerant. 

Sodium decreases the hydrothermal stability of the zeolite. It also reacts with the zeolite acid sites to reduce catalyst activity. In the regenerator, sodium is mobile. Sodium ions tend to neutralize the strongest acid sites. In a dealuminated zeolite, where the UCS is low (24.22°A to 24.25°A), the sodium can have an adverse affect on the gasoline octane (Figure 3-7). The loss of octane is attributed to the drop in the number of strong acid sites. 

Figure 3-6. Effects of rare earth on gasoline octane and yield.

The sodium in the E-cat is the sum of sodium added with the feed and sodium on the fresh catalyst. A number of catalyst suppliers report sodium as soda (Na20). Sodium deactivates the catalyst acid sites and causes collapse of the zeolite crystal structure. Sodium can also reduce the gasoline octane, as discussed earlier. 

ZSM-5 s effectiveness depends on several variables. The cat crackers that process highly paraffinic feedstock and have lower base octane will receive the greatest benefits of using ZSM-5. ZSM-5 will have little effect on improving gasoline octane in units that process naphthenic feedstock or operate at a high conversion level. 

In summary, ZSM-5 provides the refiner the flexibility to increase gasoline octane and light olefins. With the introduction of reformulated gasoline, ZSM-5 could play an important role in producing isobutylene, used as the feedstock for production of methyl tertiary butyl ether (MTBE). 

Majon, R. J. and Spielman, J., Increasing Gasoline Octane and Light Olefin Yields with ZSM-5, The Catalyst Report, Vol. 5, Issue 5, 1... 

Adding ZSM-5 catalyst additive is another process available to tlie refiner to boost production of light olefins. ZSM-5 at a typical concentration of 0.5 to 3.0 wt% is used in a number of FCC units to increase the gasoline octane and light olefins. As part of the cracking of low octane components in the gasoline, ZSM-5 also makes C. C4, and Cj olefins (see Figure 6-2). Paraffinic feedstocks respond the most to ZSM 5 catalyst additive.. 

Riser termination. Good riser termination devices, such as closed cyclones, minimize the vapor and catalyst holdup time in the reactor vessel. This reduces unnecessary thermal cracking and nonselective catalytic re-cracking of the reactor product. The benefits are a reduction in dry gas and a subsequent improvement in conversion, gasoline octane, and flexibility for processing marginal feeds. 

Feed segregation. Split feed injection involves charging a portion of the same feed to a different point in the riser. This is another tool for increasing light olefins and boosting gasoline octane. 

Engelhard Corporation, Prediction of FCCU Gasoline Octane and Light... 

Lower Conversion High Dry Gas Yield Fig. 8-11B Lower Gasoline Yield Figure 8-11C Lower Gasoline Octane Figure 8-1 ID ... 

The fresh catalyst s chemical properties also influence the FCC gasoline octane. Gasoline octane is increased by ... 

The main mechanical conditions that affect octane are the type and condition of the feed nozzles. Low-efficiency feed nozzles actually increase the gasoline octane due to promotion of thermal reactions in the mix zone. High-efficiency feed nozzles improve feed/catalyst mixing and increase the gasoline yield, but decrease gasoline octane. 

Kelly, J.J., Barrow, C.H., et. al., "Prediction of Gasoline Octane Numbers from Near-Infrared Spectral Features in the range 660-1215nm", Anal. Chem. 1989(61)313-320. 

T, C dry gas % coke % liquid yield, % olefin in gasoline, % octane number... 

These selectivities obtained with Amberlyst-15 seem to be rather optimistic in view of recent work, where only with overstoichiometric ratios high di-+tri-ether selectivity is obtained. It is also not settled why addition of tert-butanol to the reaction mixture suppresses isobutene oligomerization selectivity [34, 35], At this stage it should also be stressed that the tert-butylglycerol ethers (TBGE) mentioned are excellent substitutes for MTBE (ETBE) as gasoline octane boosting components [36]. 

MTBE is made by catalytically reacting methanol and isobutylene. The outlook for MTBE is murlty because the primary application, a gasoline octane enhancer/oxygenate, is under attack because of environmental reasons. 

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